Of the various types of machines utilized in mining operations, mining shovels are responsible for digging material from a vertical bank face or other surface that may be located in a pit at the mine site and transferring the material such as mineral ore, coal, and overburden to a dump truck or other machine for transportation. Mining shovels include a boom that extends upwards into the air and at angle with respect to the bank and a dipper assembly that is supported by the boom. The dipper assembly includes a bucket-like dipper that scoops into, fills with, and removes material from the bank and that is supported by an elongated dipper arm or handle. To enable the dipper to swing upwardly into the bank, the dipper assembly is supported by the boom in a manner that allows the dipper arm to pivot and slide with respect to the boom, hence the dipper assembly has at least two degrees of freedom with respect to the boom. The pivoting motion of the dipper upwards or downwards with respect to the boom may be referred to as hoisting. The sliding translation of the dipper arm with respect to the boom may be referred to as crowding, when proceeding in the direction of outward extension from the mining shovel, or retraction when proceeding in the direction of inward retraction or motion back towards the mining shovel.
When the dipper impacts and penetrates into the bank and fills with material, the mining shovel is subjected to severe forces and stresses. The magnitude of these forces and stresses may possibly damage the mechanical components and operational systems of the mining shovel. Further, if the dipper assembly strikes the bank at an incorrect angle of attack, “boom jacking” may occur in which the crowding dipper assembly is pushed back against the boom and may cause the boom to pivot upwardly then drop and bounces with respect to the mining shovel. To assist operators in controlling the mining shovel to accommodate these applied forces, manufacturers often configure mining shovels with computer-implemented control systems that regulate the motions and power outputs of the mining shovel during the digging operation.
One example of a control system is provided in U.S. Pat. No. 8,935,061 (“the '061 patent”). The '061 patent describes a control system which monitors forces produced by the machine including a crowd force and a hoisting force, called the hoist bail pull, used for lifting and lowering the dipper assembly into the bank. This information is used in part to control operation of a crowd motor that is responsible for crowding out and retracting in the dipper assembly to prevent the reaction forces directed backwards from attempting to tip the machine or causing a boom jack. The present disclosure is directed to providing a control system for a mining shovel or similar machine to similarly assist in operation of the machine when digging.